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抗坏血酸又称维生素C(Vc),是家蚕幼虫生长发育必需的营养物质.为探讨在非取食阶段家蚕体内还原型抗坏血酸(AsA)的来源,采用分光光度法测定家蚕在不同发育时期以及不同条件下体内的AsA含量和总抗坏血酸(TAA)含量变化,并采用实时荧光定量PCR检测AsA合成相关酶基因在家蚕不同发育阶段的表达量变化.滞育卵中AsA含量在产卵24h内,TAA含量在产卵72 h内均有所增加,此后二者的含量均不同程度降低并一直保持相对稳定;即时浸酸解除滞育蚕卵的AsA含量在产卵24 h内显著增加,且在产卵48～ 144 h一直保持较高水平,到胚胎发育后期又明显下降,但AsA含量一直高于滞育卵.幼虫期取食桑叶或添加Vc的人工饲料之后,蚕体内AsA和TAA含量均增加,幼虫在眠中或取食缺乏Vc的人工饲料及饥饿一定时间后,体内的AsA和TAA含量均明显降低,尤其是饥饿后体内的AsA含量会下降到很低的水平.蛹期的TAA含量无显著变化,但雌蛹体内AsA含量在化蛹0～24h显著升高,雄蛹体内AsA含量在化蛹0～144 h一直保持较高水平,到蛹后期才有较为明显的下降.编码AsA合成相关酶的4个同源基因BmGULO_like1、BmGULO_like2、BmALase_like1、BmALase_like2在中肠和脂肪体中的表达量总体上都是卵期及蛹期显著高于幼虫期,并且随卵和蛹的发育进程呈上升趋势.研究结果提示,家蚕胚胎发育期和蛹期的AsA来源途径,可能包括自身合成途径及由氧化型抗坏血酸(DHA)还原为AsA的途径,而在幼虫期主要从食物中吸收Vc,缺乏其他来源.“,”Ascorbic acid,also known as vitamin C (Vc),is an essential nutrient for larvae of the silkworm,Bombyx mori.To investigate the origin of reduced ascorbic acid (AsA) of silkworm in the non-feeding stage,we measured variation of AsA content and total ascorbic acid (TAA) content in silkworm at different developmental stages and under different conditions using spectrophotometry,and detected expressional changes of genes encoding enzymes involved.in AsA biosynthesis at different developmental stages of silkworm by real time fluorescence quantitative PCR.The results show that,in the diapause eggs,AsA content increased within 24 h after egg-laying and TAA content increased within 72 h after egg-laying,and then both declined at different degrees and kept steady afterwards.In the eggs of which diapause was terminated through immediate hydrochloric acid treatment,AsA content increased significantly within 24 h after egg-laying,kept at high level at 48 h to 144 h after egg-laying,and declined obviously at late stage of embryonic development,all of which was always higher than that of the diapause eggs.AsA and TAA contents increased in silkworm larvae feeding on mulberry leaves or artificial diet with Vc addition.These contents all declined obviously in molting larvae,in larvae feeding on artificial diet lacking Vc,and in larvae under fasting condition.Especially,AsA content dropped to a very low level in larvae under fasting condition.At silkworm pupal stage,TAA content had no significant change,but AsA content in female pupae increased significantly at 0 to 24 h after pupation,and that in male pupae was kept at high level at 0 to 144 h after pupation and showed remarkable reduction at late pupal stage.The expressions of 4 homologous genes (BmGULO_like1,BmGULO_like2,BmALase_like1 and BmALase_like2) encoding enzymes involved in AsA biosynthesis in midgut and fat body at egg stage and pupal stage were as a whole significantly higher than those at larval stage.Moreover,their expressions showed a rising trend with the development of eggs and pupae.Our results indicate that,at embryonic developmental stage and pupal stage of silkworm,AsA may be produced via de novo synthesis and via reduction of oxidized ascorbic acid (DHA),while silkworm larvae mainly absorb Vc from diet and lack other sources.